Difference: 1. CHAR is fixed length, while the VARCHAR2 length can vary, for example, store the string "abc", for CHAR (20), that you stored the characters will account for 20 bytes (including 17 null characters), The same VARCHAR2 (20) onl

EJB3 is developed, JBoss to connect to MySQL database appear 09:40:30,890 WARN [org.jboss.resource.connectionmanager.JBossManagedConnectionPool] Throwable while attempting to get a new connection: null: org.jboss.resource.JBossResourceException: Coul

@ @ Rowcount: This variable records the number of records affected by the last operation, including insert, you can determine if it is not> 0 @ @ Error, @ @ sqlstatus Using an insert statement in a stored procedure executed successfully implement

1, poorly written using bind variables: select * from basetab where msisdn = '13800138000 ' The correct wording: select * from basetab where msisdn =: 1 Using preparedstatement in jdbc 2, do not frequently commit Not the right way: insert int

In oracle, for the large amount of data in the database in the delete, it is very slow speed. In fact, there is another way to delete data, is that you can use truncate to delete data in the table. However, this method is deleted, although the speed

1, there is an expression of the field can not use an index of bad habits: select * from mydata where 100> salary Select * from mydate where salary +1> 100; Good habits: select * from mydata where salary <100 2, to avoid the word index value

Sql code MERGE INTO CRPROPTREND T1 USING DUAL T2 ON (T1.URIMD5 = "abc") WHEN MATCHED THEN INSERT VALUES (...) WHEN NOT MATCHED THEN UPDATE SET ...; Sql code - This query is not editable, but generally faster Select URIMD5, count (*) from RU

PL / SQL functions and group functions Detailed single Function is a zero or more parameters and a return value of the program. In a series of SQL, Oracle built-in functions that can be called SQL or PL / SQL statements, functions, divided into two c

Today, when performed during the procedure, using a PL / SQL tool in the test, debug methods of execution, because there are input parameters, but reported an error: "Note: debugging requires the debug connect session system privilege". The

Oracle Corporation is the world's largest information management software and services provider, established in 1977, is headquartered in California, USA Redwood shore. 2000 fiscal year (June 1999 to May 2000) turnover of $ 10.1 billion, another

The latest version of Oracle 11g R2 version is, many online installation instructions are 9i or 10g, and I introduced RHEL5.5 installed in accordance with Oracle 11gR2 is always a problem, then see the official document describes the CD's doc dir

Each oracle database should have at least one database administrator (dba), for a small database, a dba enough, but for a large database may take many different dba assume management responsibilities were (1) the database administrator (dba) responsi

Directive controls which will be used in a particular directory server features. Options property has a very special feature: If you do not use "+" or "-" to increase or decrease a function of time, before the definition of each o

According to the hibernate documentation, there are two ways to achieve the entity object's primary key auto-growth. The first: the growth strategy is to set the ID sequence, while the name of the specified sequence, it is best to build a table f

Automatic backup of MySQL under linux tools - Second Edition Second Edition program on the basis of the first edition made perfect. Including custom database host and backup paths, support for backing up multiple databases, regardless of how many dat

We will discuss a variety of used to access the ORACLE database DDL and TCL statement. Inquiry SELECT statement is used to query data from the database, when the PL / SQL using the SELECT statement, to be used in conjunction with the INTO clause, the

MySQL default idle wait time is 8 hours, if idle for more than 8 hours, it will throw "Communications link failure due to underlying exception" exception, modify / etc / my.cnf (windows under the my.ini), the timeout is set to 30 days, in [

ORIGINAL: http://jun-li-leo.iteye.com/blog/751981 We often want to write code to access the page recorded the source page address and the user's access to IP, it will use the following content. js method to obtain the source page address: var url

Interfaces and communication protocols has been widely used in computer serial communications, RS232 engaged in application development professionals have been the traditional RS232 serial interface, showing more and more dissatisfied. In industrial

MySQL's default encoding is Latin1, does not support Chinese, then how to modify MySQL's default encoding it, following the UTF-8 as an example to illustrate the need for attention is very much a place to change, corresponding changes are als

identity: the identifier generated by the underlying database. identity is generated by the database itself, but the primary key must be set to self-growth, low-level database support is a prerequisite for growth of field types automatically incremen

mybatis Although foreign key in the query field, but the primary key table field is not necessary to JOIN query sql statement <!-- According to the user ID query one man's treasure --> <select parameterType="string" resultMap="huntTreasureLo

Although this book is the English original, but a lot of code and illustrations, is a full-color illustrations Oh. Basically you can read, if necessary, or see it. Focal.Press.Flash.Mobile.Developing.Android.and.iOS.Applications.Mar.2011.rar

The bank's paid to do the query interface, when using httpclient query, use getMethod assembled the correct data, executeMethod, return the statusCode of 200, indicating the call has been normal, but the data returned is empty, Whether it is html

1 sql query id of a field is empty select * from table where id is null; 2 sql query id of a field is not empty select * from table where id is not null; Or select * from table where id <> null; / / select * from table where len (id)> 1; / /

Cursor for loop cursor display shows a quick use, it uses a for loop in order to read the result set of rows of data, when the cycle began to form, the cursor automatically open (not open), each cycle of a system to automatically read the current cur

9i provides a method of online redefine a table that lets you basically do not affect the original table in the DML to modify the table structure. In fact, online table redefinition is not entirely online redefinition, Exchange in the final table wil

Wrote a backup script mysql under linux this is the first version, only support a database backup every day 14:00 to run this script with a timer to automatically back up a bit. Follow-up will do to support multiple database backup, backup failure me

Identifying SQL Statements for Later Plan Retrieval labeled SQL statement after the plan to facilitate retrieval (page 171) If you want to retrieve a statement that was executed in the past, you can retrieve the SQL_ID and CHILD_NUMBER from V $ SQL a

Reprinted from: http://www.linuxidc.com/Linux/2010-06/26450.htm Morning the MySQL test data written into the 240 000 in the afternoon to find the database file is not found, only to find a size of only 9K. Frm file, but frm file is not a database fil